Should Mayor Connect Brooklyn to Queens With a Waterfront Streetcar Line?

A story in The New York Times suggests Mayor de Blasio can do an end run around Albany and forge a public transportation route to meet new needs with a modern streetcar line along the waterfront from Brooklyn to Queens. The line would make it easier for residents to get around Brooklyn; tie together transit starved areas such as Red Hook, Greenpoint and the Navy Yard; connect to ferry, bus and subway routes; and link Brooklyn to Queens.

The author estimates it would cost somewhere around $600,000,000 or so. Now that Brooklyn is less Manhattan-centric, do you think this is an idea whose time has come, or should we just improve existing bus and subway service?